The present invention relates to a wiring pattern inspecting method and a system for carrying out the same using an electromagnetic wave, such as x-rays, or an ultrasonic wave and capable of inspecting wiring patterns (circuit patterns) formed in a plurality of layers on a printed wiring board or the like for chipped defects including internal defects, and nodular defects (three-dimensional defects).
A wiring pattern inspecting technique disclosed in JP-A No. 5-215694, JP-A No. 7-43320 (corresponding to U.S. application Ser. No. 08/212763), now U.S. Pat. No. 5,754,621 (Prior art 1) is capable of accurately inspecting a wiring pattern (circuit pattern) formed on a printed wiring board for defects in the direction of thickness (three-dimensional defects) including chipped defects on the bottom of the wiring pattern by using, for example, an x-ray transmission image in distinction from a case where there is no wiring pattern.
A wiring pattern inspecting technique for detecting disconnection defects including virtual disconnection defects, and short circuit defects including virtual short circuit defects in a wiring pattern disclosed in JP-A No. 59-192945 (corresponding to U.S. Pat. No. 4,654,583), JP-A No. 61-86638 (corresponding to U.S. Pat. No. 4,953,224), JP-A No. 1-230183 (coresponding to U.S. Pat. No. 5,301,248) (Prior art 2) comprises taking an optical image of a printed wiring pattern, converting the optical image into an electric signal (image signal), converting the electric signal (image signal) into a binary image signal, examining the relation in connection between two selected points (aimed points) to produce connection data expressing the relation in connection by a pair of numbers assigned to the selected points, and comparing the connection data with reference data expressing the numbers assigned to the points in the relation in connection produced on the basis of design information or the like in a circular list structure.
A wiring pattern inspecting technique for inspecting a wiring pattern for defects disclosed in JP-A No. 62-131391 (Prior art 3) comprises extracting singular points on skeletal lines of a wiring pattern (circuit pattern), such as end points of the skeletal lines and branching points, storing the coordinates of the singular points as information about the inspected wiring pattern, reading out coordinate information about the coordinates of the singular points, and comparing the coordinate information with reference coordinate information about reference singular points extracted from a reference wiring pattern to detect disconnection defects and short circuit defects from the difference between the wiring pattern formed on the printed wiring board and the reference wiring pattern. An X-ray imaging system is disclosed in Japanese Application Laid-Open No. 06-188092.
All those prior art techniques take nothing into consideration about surely inspecting wiring patterns superposed on a printed wiring board or the like for defects without overlooking internal defects (three-dimensional defects) that occur on the bottom of the wiring patterns.